Transmission shaft and method and device for the production thereof

ABSTRACT

A transmission shaft of a countershaft-type manual transmission is constructed from a plurality of hollow shaft portions which are butt press welded to one another, at least two of which hollow shaft portions are provided in each instance with at least one helical toothing of a fixed wheel of a spur gear stage. The hollow shaft portions provided with a helical toothing are connected to the respective adjacent hollow shaft portion in each instance so as to be rotated by a correction angle (Δα) around their center axis in proportion to a deviation (Δx) from their axial target position, wherein the ratio between the correction angle (Δα) and the axial deviation (Δx) corresponds to the pitch (s) of the helical toothing (Δα/Δx=s).

PRIORITY CLAIM

This is a Divisional Application of Ser. No. 15/103,325, filed Jul. 10,2016. Priority is claimed on the following application: Country:Germany, Application No.: 10 2013 225 714.7, filed: Dec. 12, 2013, thecontent of which is incorporated herein in its entirety by reference.

1. FIELD OF THE INVENTION

The invention is directed to a transmission shaft of a countershaft-typemanual transmission which forms one of at least two substantiallyidentical countershafts and which is constructed from a plurality ofhollow shaft portions which are butt press welded to one another, atleast two of which hollow shaft portions are provided in each instancewith at least one helical toothing of a fixed wheel of a spur gearstage. The invention is further directed to a method and to a device forthe production of a transmission shaft of this type from a plurality ofpress welded hollow shaft portions.

2. BACKGROUND OF THE INVENTION

Transmission shafts of countershaft-type manual transmissions such asinput shafts, countershafts, main shafts or output shafts are usuallyconstructed as massive solid shafts. The fixed wheels of spur gearstages such as input constants, switchable transmission gear stages oroutput constants which are arranged on these transmission shafts areoften produced as separate component parts which are pressed onto thetransmission shaft at correspondingly constructed bearing seats and arepreferably additionally secured by positive engagement, for example, bypinning, against axial movement. However, it is also known that theteeth of fixed wheels can be incorporated in corresponding annularstrips of the transmission shaft through suitable machining processessuch as rolling or milling. In this case, the fixed wheels areintegrally connected to the respective transmission shaft. However, adisadvantage in solid transmission shafts of this kind consists in theirlarge mass, which increases the weight of the manual transmission inquestion, and in the resulting high mass moment of inertia, so that therespective transmission shaft must be retarded or accelerated againstthe resistance of this high mass moment of inertia during ashift-dependent synchronizing of the target gear insofar as thistransmission shaft is an input shaft or countershaft. Further, theincreased use of material increases costs.

To avoid these disadvantages, it has been suggested to constructtransmission shafts as hollow shafts without compromising strength.These are known as assembled transmission shafts and are constructedfrom a plurality of hollow shaft portions which are connected to oneanother by frictional engagement, positive engagement or bonding.

A corresponding transmission shaft comprising three hollow shaftportions is described in DE 10 2005 036 681 A1. The hollow shaftportions which are preferably produced by massive forming are joinedtogether by laser welding or by spin welding at abutted annularsurfaces. The axially outer hollow shaft portions have been closed attheir free ends by swaging. The fixed wheels arranged on thetransmission shaft are produced as separate component parts and arepressed on associated bearing seats of the relevant hollow shaftportions.

A method for the production of a hollow transmission shaft and a hollowtransmission shaft produced according to this method are known from DE10 2006 016 099 B4. The hollow transmission shaft is built of aplurality of axially successive hollow shaft portions, at least two ofwhich hollow shaft portions are provided, respectively, with a toothingof a fixed wheel arranged on the hollow transmission shaft. The hollowshaft portions are connected to one another at abutted annular surfacesby spin welding. The teeth of the relevant hollow shaft portions havebeen finish-machined before being joined. The hollow shaft portions arejoined together with high precision with respect to theircircumferential target angular position and their radial and axialoffset. However, DE 10 2006 016 099 B4 does not specifically show howthis is to be achieved.

DE 10 2008 064 267 A1 describes a transmission shaft which isconstructed as a hollow shaft and which likewise comprises a pluralityof hollow shaft portions and a method for producing it. For centeringrelative to one another, the hollow shaft portions have plug-in contoursat the ends facing one another. These plug-in contours engage coaxiallyone inside the other and have a plurality of conically inclined frictioncontact surfaces which are offset in a steplike manner for connectingthe hollow shaft portions by spin welding. Further, the hollow shaftportions have annular radial stop surfaces at the edge of the plug-incontours for axial alignment of the hollow shaft portions. The hollowshaft portions can be connected to one another with high radial andaxial precision through the shape of the plug-in contours, but anelaborate mechanical machining of the hollow shaft portions is requiredfor producing the plug-in contours with the friction surfaces and stopsurfaces. Further, the arrangement of the plug-in contours requires anunfavorably large thickness of the hollow shaft portions.

Particularly when a countershaft-type manual transmission such as thatprovided in the present instance has at least two substantiallyidentical countershafts which are each constructed from a plurality ofhollow shaft portions which are butt press welded to one another andpartially provided with a helical toothing of a fixed wheel of a spurgear stage, the problem arises of an accurate alignment of thecircumferential target angular position of the hollow shaft portionsprovided with a helical toothing. Two countershafts in acountershaft-type manual transmission serve to distribute a torque to betransmitted to two parallel force transmission paths and accordingly toachieve a relatively compact and lightweight construction and a hightransmission efficiency of the respective manual transmission. An exactalignment of the circumferential angular position of the toothings ofthe fixed wheels is required for a uniform distribution of the torque tobe transmitted, since these toothings are in toothed engagement pairwisein each instance with an individual counter-gearwheel or anothertransmission shaft, for example, a fixed wheel of an input constant thatis arranged on an input shaft so as to be fixed with respect to rotationrelative to it or a loose wheel of a switchable transmission gear stagewhich is rotatably supported on an intermediate shaft or output shaft.

In the known press welding methods like spin welding and electric arcwelding with magnetically moving arcs, the hollow shaft portions to beconnected to one another are joined together axially with high pressingforce after the contact surfaces facing one another are plasticized,which necessarily entails a certain axial tolerance. Accordingly, theaxial joining together of the hollow shaft portions may result in adeviation of the toothings arranged thereon from their axial targetposition, which deviation has the effect of twisting the respectivefixed wheels or hollow shaft portions in the rest of the implementationas helical toothings. As a result, there is no longer an optimaltoothing engagement with the associated counter-gearwheel.

Therefore, it is an object of the invention to propose a transmissionshaft of the type mentioned above which is constructed from a pluralityof hollow shaft portions which are butt press welded to one another andwhose hollow shaft portions which are provided with at least one helicaltoothing of a fixed wheel of a spur gear stage are exactly axiallyaligned in joined condition with respect to their circumferential targetangular position. Further, a method and a device for producing atransmission shaft of this type from a plurality of hollow shaftportions which are press welded to one another are described.

SUMMARY OF THE INVENTION

Therefore, the invention is directed first to a transmission shaft of acountershaft-type manual transmission which forms one of at least twosubstantially identical countershafts and which is constructed from aplurality of hollow shaft portions which are butt press welded to oneanother, at least two of which hollow shaft portions are provided ineach instance with at least one helical toothing of a fixed wheel of aspur gear stage. In order to meet this object with respect to thetransmission shaft, it is further provided that the hollow shaftportions provided with a helical toothing are connected to therespective adjacent hollow shaft portion in each instance so as to berotated by a correction angle Δα around their center axis in proportionto a deviation Δx from their axial target position, where the ratiobetween the correction angle Δα and the axial deviation Δx correspondsto the pitch s of the helical toothing (Δα/Δx=s).

Accordingly, the invention is based on a transmission shaft of acountershaft-type manual transmission which forms one of at least twosubstantially identical countershafts and which is constructed from aplurality of hollow shaft portions which are butt press welded to oneanother. At least two of the hollow shaft portions are provided,respectively, with at least one helical toothing of a fixed wheel of aspur gear stage.

The teeth of the at least two countershafts engage identically in therespective shared counter-gearwheel due to the fact that the hollowshaft portions provided with a helical toothing are connected to therespective adjacent hollow shaft portion in each instance so as to berotated by a correction angle Δα around their center axis in proportionto a deviation Δx from their axial target position corresponding in eachinstance to the pitch s of their helical toothing. The counter-gearwheelcan be, for example, the fixed wheel of an input constant, which fixedwheel is arranged on the input shaft of the transmission so as to befixed with respect to rotation relative to it, or the loose wheel of aswitchable transmission gear stage, which loose wheel is rotatablysupported on the output shaft or main shaft of the transmission and canbe connected to the latter so as to be fixed with respect to rotationrelative to it via an associated gear clutch. As a result of the optimaltoothing engagement of the toothings of the at least two countershaftswith the respective counter-gearwheel, the flow of force takes place inequal parts via the at least two force transmission paths, eachcomprising one of the countershafts.

The hollow shaft portions of the transmission shaft are preferablyconnected to one another by spin welding. In this press welding method,the heating of the material is limited to a narrow region close to thefacing contact surfaces of the hollow shaft portions and is identicalalong the circumference, i.e., rotationally symmetrical with respect tothe center axis of the hollow shaft portions. Therefore, a thermallyinduced warping of the hollow shaft portions and resulting bending ofthe transmission shaft are extensively ruled out.

For the same reasons, the hollow shaft portions can also be connected toone another by electric arc welding with magnetically moving arcs.

Since the above-mentioned press welding methods are carried out with acertain axial tolerance when joining the hollow shaft portions together,the helical toothings of the hollow shaft portions are preferablycarried out with an axial excess width relative to theircounter-gearwheels to compensate for the axial tolerances. This ensuresthat the toothing engagement between the toothings of the hollow shaftportions and the associated counter-gearwheels always takes place overthe full tooth width of the counter-gearwheels independently of theexisting axial tolerances.

As is conventional, per se, the transmission shaft has a bearing supportwith a fixed bearing and a loose bearing. The fixed bearing ispreferably arranged at the first hollow shaft portion to which thesecond hollow shaft portion is fastened, and the loose bearing ispreferably arranged at the last hollow shaft portion which is fastenedto the penultimate hollow shaft portion. By arranging the fixed bearingat the first hollow shaft portion, the latter is fixed in its axialtarget position in the transmission housing of the manual transmission.Joint-related axial displacements of the rest of the hollow shaftportions are then made possible and compensated in a bearing-relatedmanner by the loose bearing mounted at the last hollow shaft portion.

However, it can also be provided for the bearing support of thetransmission shaft with a fixed bearing and a loose bearing that thefixed bearing is arranged at the last hollow shaft portion which isfastened to the penultimate hollow shaft portion, and the loose bearingis arranged at the first hollow shaft portion to which the second hollowshaft portion is fastened. Accordingly, the last hollow shaft portion isfixed in its axial target position in the transmission housing of themanual transmission via the fixed bearing. The rest of the hollow shaftportions are then rotated back correspondingly through the correction ofthe circumferential rotational angle positions carried out during theaxial joining so that an optimal toothing engagement with thecounter-gearwheels also results in this arrangement of the fixed bearingand loose bearing.

With respect to the construction of the above-mentioned bearings, it ispreferably provided that the fixed bearing is constructed as a groovedball bearing and the loose bearing is constructed as a cylindricalroller bearing.

The object relating to the method for producing a transmission shaft ismet in that the hollow shaft portions provided with a helical toothingare rotated by a correction angle Δα around their center axis inproportion to a deviation Δx from their axial target position in eachinstance after the plasticizing of the material at the facing contactsurfaces during the axial joining together of the adjacent hollow shaftportions, where the ratio between the correction angle Δα and the axialdeviation Δx corresponds to the pitch s of the helical toothing(Δα/Δx=s).

Accordingly, this method relates to the production of a transmissionshaft of a countershaft-type manual transmission which forms one of atleast two substantially identical countershafts and which is constructedfrom a plurality of hollow shaft portions which are butt press welded toone another. At least two of the hollow shaft portions are provided ineach instance with at least one helical toothing of a fixed wheel of aspur gear stage.

In order to achieve an optimal toothing engagement of the helicaltoothings of the at least two countershafts with the associatedcounter-gearwheels and, accordingly, an even distribution of thetransmitted torque to the two force transmission paths comprising onecountershaft in each instance, the hollow shaft portions provided with ahelical toothing are rotated according to the method by a correctionangle Δα around their center axis in proportion to a deviation Δx fromtheir axial target position in each instance after the plasticizing ofthe material at the facing contact surfaces during the axial joining tothe adjacent hollow shaft portion. In this regard, the ratio between thecorrection angle Δα and the axial deviation Δx corresponds in eachinstance to the pitch s of the helical toothing (Δα/Δx=s) so that theeffect of joint-related axial displacements of the hollow shaft portionson the toothing engagement with the counter-gearwheels is compensated.

The rotation of the hollow shaft portions can be carried out by means ofa rotary drive in driving connection with a pressure die which receivesthe respective hollow shaft portion at its end. This can be a separaterotary motor which can be controlled mechanically independently of theaxial forward feed during the joining of the hollow shaft portions.However, it can also be a passive rotary drive which is coupled with theaxial forward feed through an engine-internal coupling gear stage.Coupling gear stages of this kind, by which a rotary drive is coupledwith an axial forward feed, are known from lathes, for example.

It is preferable, however, that the rotation of the hollow shaftportions takes place by a positive-engagement rotary guide which isarranged between a cylindrical portion of the pressure die receiving therespective hollow shaft portion at its end and a stationary bore holeand which has the pitch s of the helical toothing. The expenditure onapparatus for a separate rotary drive of the pressure die and for anengine-internal coupling gear stage can be avoided with this rotaryguide of the pressure die.

The hollow shaft portions are preferably connected to one another byspin welding. The plasticizing of the contact surfaces facing oneanother is carried out in each instance through rotation of a hollowshaft portion which is not axially displaceable and by a simultaneousaxially pressing of the nonrotatable hollow shaft portion against therotatable hollow shaft portion with moderate pressing force via thepressure die, and the joining together of the hollow shaft portions iscarried out after the plasticizing of the contact surfaces by axiallypressing the nonrotatable hollow shaft portion against the rotatablehollow shaft portion with high pressing force by the pressure die.

Alternatively, the hollow shaft portions can also be connected to oneanother through electric arc welding with magnetically moving arcs, andthe plasticizing of the contact surfaces facing one another is carriedout in each instance through a magnetically controlled arc circulatingbetween stationary poles and the region of the contact surfaces, and thejoining together of the hollow shaft portions is carried out after theplasticizing of the contact surfaces by axially pressing the one hollowshaft portion against the other hollow shaft portion with high pressingforce by the pressure die.

The object of the invention relating to the device for producing atransmission shaft is met in that a pressure die is provided with afirst receptacle for a hollow shaft portion which is rotatable aroundits center axis depending on requirements in proportion to its axialforward feed.

The above-mentioned device serves for producing a transmission shaft ofa countershaft-type manual transmission which forms one of at least twosubstantially identical countershafts and which is constructed from aplurality of hollow shaft portions which are butt press welded to oneanother. At least two of the hollow shaft portions are provided in eachinstance with at least one helical toothing of a fixed wheel of a spurgear stage. When a hollow shaft portion provided with at least onehelical toothing of a fixed wheel is axially joined to an adjacenthollow shaft portion, then in order to enable a rotation of the hollowshaft portion corresponding to an axial offset occurring as a result ofthe joining, the device is provided with a pressure die having a firstreceptacle for the hollow shaft portion to be joined, and the pressuredie is rotatable around its center axis in proportion to its axialforward feed if required.

The pressure die 27 can be actively rotatable by a controllable rotarymotor 26, i.e., a rotary motor which can be switched on and switched offand which can be regulated with respect to its rotational speed.However, this requires a separate rotary motor with a correspondingcontrol device. (FIG. 3 )

Alternatively, the pressure die 27 can also be passively rotatable inproportion to the axial forward feed by an engine-internal coupling gearstage which can be switched on and switched off and which has a gearratio corresponding to the pitch of the helical toothing. Coupling gearstages of this type by which a rotary drive is coupled to an axialforward feed are known from lathes, for example.

However, it is preferable that the pressure die 27 is passivelyrotatable by a positive-engagement rotary guide 29 which can be switchedon and switched off and which is arranged between a cylindrical portionof the pressure die and a stationary bore hole 39 and has the pitch s ofthe helical toothing. A rotary guide of the pressure die such as this isconstructed in a relatively simple manner, can be produced inexpensivelyand incurs a particularly low expenditure on apparatus and controlcompared to the constructions mentioned above.

The rotary guide is formed, for example, from at least one radiallyprotruding guide strip arranged at the cylindrical portion of thepressure die and at least one guide groove arranged in the stationarybore hole 39, and the guide strip 31 and guide groove 40 each have thepitch of the helical toothing, and the guide strip 31 engages in theguide groove 40 when the rotary guide 29 is moved in. (FIG. 3 )

The device according to the invention can be configured to connect thehollow shaft portions by spin welding and can have a further rotatablereceptacle for an adjacent hollow shaft portion which is in drivingconnection with a controllable rotary drive and a controllable brake 37for plasticizing the facing contact surfaces of the two adjacent hollowshaft portions. A typical device for spin welding tubular workpieceswithout a rotary drive of the workpiece to be joined is known from, DE195 23 240 C1, for example, the entire content of which is incorporatedherein by reference.

Alternatively, the device according to the invention can also beconstructed for connecting the hollow shaft portions by electric arcwelding with magnetically controlled arcs and can have a furtherreceptacle for an adjacent hollow shaft portion and an annularpole-and-coil arrangement 38 for plasticizing the facing contactsurfaces of the two adjacent hollow shaft portions. (FIG. 5 ) A typicaldevice for electric arc welding with magnetically controlled arcswithout a rotary drive of the workpiece to be joined is described in DE30 18 199 C2, for example, the content of which is incorporated hereinby reference in its entirety.

BRIEF DESCRIPTION OF THE DRAWINGS

To further illustrate the invention, the description is accompanied bydrawings with embodiment examples. The drawings show:

FIG. 1 is a perspective sectional view of a transmission shaft accordingto the invention;

FIG. 2 is a full view in perspective of the transmission shaft accordingto FIG. 1 with bearings;

FIG. 3 shows a device for producing a transmission shaft according toFIGS. 1 and 2 in a schematic perspective view;

FIG. 4 shows a known manual transmission for utilizing the transmissionshaft according to FIG. 1 and FIG. 2 in longitudinal central section;and

FIG. 5 shows a schematic view of another device for producing atransmission shaft according to FIGS. 1 and 2 .

DETAILED DESCRIPTION OF THE PRESENTLY PREFERRED EMBODIMENTS

A transmission shaft 1, shown in longitudinal section as an embodimentexample in FIG. 1 , forms one of at least two substantially identicalcountershafts of a countershaft-type manual transmission. Thetransmission shaft 1 according to the invention is formed as a hollowshaft and is constructed from four hollow shaft portions 2, 3, 4, 5which are butt press welded to one another. Each of these four hollowshaft portions 2, 3, 4, 5 is integrally provided with at least onehelical toothing 6, 7, 8, 9, 10 and has, in each instance, annularcontact surfaces 11, 12, 13, 14, 15, 16 facing one another. As iscustomary, the helical toothings 6, 7, 8, 9, 10 have an identical pitchs, as indicated in the drawing, so that the axial forces occurringwithin the transmission shaft 1 during the transmission of force arecanceled and need not be absorbed via a bearing.

A first helical toothing 6 arranged on the first hollow shaft portion 2forms the fixed wheel of a first spur gear stage, which fixed wheel isarranged on the transmission shaft 1. A wider, second helical toothing 7arranged on the first hollow shaft portion 2 forms the shared fixedwheel of two further spur gear stages of the manual transmission, whichshared fixed wheel is arranged on the transmission shaft 1. A thirdhelical toothing 8 arranged on the second hollow shaft portion 3 formsthe fixed wheel of a fourth spur gear stage of the manual transmission,which fixed wheel is arranged on the transmission shaft 1. A fourthhelical toothing 9 arranged on the third hollow shaft portion 4 formsthe fixed wheel of a fifth spur gear stage of the manual transmission,which fixed wheel is arranged on the transmission shaft 1. A fifthhelical toothing 10 arranged on the fourth hollow shaft portion 5 formsthe fixed wheel of a sixth spur gear stage of the manual transmission,which fixed wheel is arranged on the transmission shaft 1.

The second hollow shaft portion 3 was joined to the first hollow shaftportion 2 after plasticizing the material at the contact surfaces 11, 12facing one another by axial pressing with high pressing force. Whileaxially joining to the first hollow shaft portion 2, the second hollowshaft portion 3 was rotated around the center axis 19 by a correctionangle Δα₃ in proportion to an individual deviation Δx₃ from its axialtarget position, where the ratio between the correction angle Δα₃ andthe axial deviation Δx₃ corresponds to the pitch s of the helicaltoothing 8 (Δα/Δx=s).

The third hollow shaft portion 4 was joined to the second hollow shaftportion 3 after plasticizing the material at the contact surfaces 13, 14facing one another by axial pressing with high pressing force. Whileaxially joining to the second hollow shaft portion 3, the third hollowshaft portion 4 was rotated around the center axis 19 by a correctionangle Δα₂ in proportion to an individual deviation Δx₂ from its axialtarget position also corresponding to the pitch s of the helicaltoothing 9.

The fourth hollow shaft portion 5 was joined to the third hollow shaftportion 4 after plasticizing the material at the contact surfaces 15, 16facing one another by axial pressing with high pressing force. Whileaxially joining to the third hollow shaft portion 4, the fourth hollowshaft portion 5 was also rotated corresponding to the pitch s of thehelical toothing 10 around the center axis 19 by a correction angle Δα₁in proportion to a deviation Δx₁ from its axial target position.

As a result of the respective rotation of the hollow shaft portions 3,4, 5 to be joined, the respective deviation Δx of the hollow shaftportions 3, 4, 5 from their axial target position with respect to thecircumferential angular position of the helical toothings 8, 9, 10 iscompensated during the axial joining process resulting in an optimaltoothing engagement of these helical toothings 8, 9, 10 with theassociated counter-gearwheels of the manual transmission.

The transmission shaft 1 is rotatably supported in a transmissionhousing in a manner known per se via a fixed bearing 20 and a loosebearing 22. As can be seen from the perspective views of FIG. 1 and FIG.2 , the fixed bearing 20 which is formed as a grooved ball bearing 21 isarranged at an inner bearing seat 17 of the fourth hollow shaft portion5. The loose bearing 22 which is formed as a cylindrical roller bearing23 is correspondingly arranged at an outer bearing seat 18 of the firsthollow shaft portion 2 at the axially opposite end of the transmissionshaft 1. Since the fourth hollow shaft portion 5 and helical toothing 10thereof are correctly axially positioned in the transmission housingwith this arrangement of the bearings 20, 22, the correction of thecircumferential angular position carried out during the process of axialjoining the hollow shaft portions 3, 4, 5 now results in a correspondingturning back of the helical toothings 6, 7, 8, 9 of the first threehollow shaft portions 2, 3, 4 so that an optimal toothing engagement ofthese helical toothings 6, 7, 8, 9 with the associatedcounter-gearwheels of the manual transmission is also achieved.

A preferred embodiment form of a device 24 for producing a transmissionshaft according to FIG. 1 and FIG. 2 is shown schematically in FIG. 3 .The device 24 serves to connect the hollow shaft portions 2, 3, 4, 5 byspin welding.

The device 24 has a first receptacle 25 for a hollow shaft portion 2, 3,4 which is in driving connection with a controllable rotary drive 26 anda controllable brake 37, for plasticizing the facing contact surfaces11, 12; 13, 14; 15, 16 of the respective adjacent hollow shaft portions2, 3; 3, 4; 4, 5. The first receptacle 25 is constructed as a clampingchuck in the present instance. The device 24 further has a pressure die27 with a second receptacle 28 for a hollow shaft portion 3, 4, 5 to bejoined, which hollow shaft portion 3, 4, 5 is rotatable around itscenter axis according to requirements in proportion to its axial forwardfeed. By means of the pressure die 27, the hollow shaft portion 3, 4, 5to be joined is initially pressed against the adjacent hollow shaftportion 2, 3, 4 with moderate pressing force for plasticizing thematerial in the region of the contact surfaces 11, 12; 13, 14; 15, 16and after plasticizing is pressed against the adjacent hollow shaftportion 2, 3, 4 with high pressing force. The second receptacle 28 isconstructed as a stationary radial guide in the present instance.

A positive-engagement rotary guide 29 is provided for rotating thepressure die 27 and is arranged between a cylindrical portion 30 of thepressure die 27 and a stationary bore hole 39, and has the pitch s ofthe helical toothings 6, 7, 8, 9, 10. The rotary guide 29 comprises aplurality of radially protruding guide strips 31 which are arranged onthe cylindrical portion 30 of the pressure die 27 and correspondingguide grooves 40 (indicated by dotted lines in FIG. 3 ) which arearranged in the stationary bore hole and in which the guide strips 31engage. The guide strips 31 and guide grooves 40 have the pitch s of thehelical toothings 6, 7, 8, 9, 10 in each instance.

In the illustration in FIG. 3 , the first hollow shaft portion 2 isfastened in the receptacle 25 of the rotary drive 26. The second hollowshaft portion 3 is already fastened to the first hollow shaft portion 2,and the third hollow shaft portion 4 is already joined to the secondhollow shaft portion 3. The fourth hollow shaft portion 5 is fixed inthe receptacle 28 of the pressure die 27.

After the hollow shaft portions 4, 5 which are initially not yetconnected are moved together axially, the third hollow shaft portion 4is rotated by means of the rotary drive 26 and the fourth hollow shaftportion 5 is pressed against the third hollow shaft portion 4 withmoderate pressing force by the pressure die 27. After the plasticizingof the material in the region of the contact surfaces which face oneanother, the third hollow shaft portion 4 is braked and fixed in correctposition with respect to its circumferential angular position. Thefourth hollow shaft portion 5 is then pressed against the third hollowshaft portion 4 with high pressing force by the pressure die 27 so thatthese two hollow shaft portions 4, 5 are connected to one another.

A deviation of the fourth hollow shaft portion 5 from its axial targetposition occurring during the axial joining process causes aproportionate rotation of the fourth hollow shaft portion 5 around thecenter axis 19 due to the rotary guide 29. Since the ratio between thecorrection angle Δα of the rotation and the deviation Δx from the axialtarget position of the fourth hollow shaft portion 5 corresponds to thepitch s of the helical toothing 10 (Δα/Δx=s), the fourth hollow shaftportion 5 is accordingly optimally aligned for an optimal toothingengagement of the helical toothing 10 with the associatedcounter-gearwheel. This also applies, of course, to the second hollowshaft portion 3 previously joined to the first hollow shaft portion 2and to the third hollow shaft portion 4 previously joined to the secondhollow shaft portion 3.

A known compound-type AS-Tronic-series manual transmission 32 by thepresent Applicant is shown in FIG. 4 in longitudinal central section asa use example for the transmission shaft 1 according to the invention.The manual transmission 32 has a countershaft-type main transmission 33and a planetary range group 34 downstream of the main transmission 33 indrive direction. The main transmission 33 has two substantiallyidentical countershafts 35, 36 with a plurality of helical teeth offixed wheels of associated spur gear stages. Therefore, the twocountershafts 35, 36 of this manual transmission 32 are particularlysuitable to be constructed in accordance with the transmission shaft 1according to the invention and to be produced according to the describedmethod.

Thus, while there have shown and described and pointed out fundamentalnovel features of the invention as applied to a preferred embodimentthereof, it will be understood that various omissions and substitutionsand changes in the form and details of the devices illustrated, and intheir operation, may be made by those skilled in the art withoutdeparting from the spirit of the invention. For example, it is expresslyintended that all combinations of those elements and/or method stepswhich perform substantially the same function in substantially the sameway to achieve the same results are within the scope of the invention.Moreover, it should be recognized that structures and/or elements and/ormethod steps shown and/or described in connection with any disclosedform or embodiment of the invention may be incorporated in any otherdisclosed or described or suggested form or embodiment as a generalmatter of design choice. It is the intention, therefore, to be limitedonly as indicated by the scope of the claims appended hereto.

What is claimed is:
 1. A device for producing a transmission shaft of acountershaft-type manual transmission which forms one of at least twosubstantially identical countershafts and which is constructed from aplurality of hollow shaft portions (2; 3; 4; 5) which are butt presswelded to one another, at least two of which hollow shaft portions (2;3; 4; 5) are provided in each instance with at least one helicaltoothing (6, 7, 8, 9, 10) of a fixed wheel of a spur gear stage, saiddevice comprising: a pressure die (27) with a first receptacle (28) fora hollow shaft portion (3; 4; 5), said pressure die (27) being rotatablearound a center axis (19) of said pressure die (27) in proportion to anaxial forward feed of said pressure die (27), said pressure die (27)being passively rotatable by a positive-engagement rotary guide (29)which can be switched on and switched off and which is arranged radiallybetween a cylindrical portion (30) of the pressure die (27) and astationary bore hole (39), said rotary guide (29) comprising: at leastone radially protruding guide strip (31) arranged at the cylindricalportion (30) of the pressure die (27), and at least one guide groove(40) arranged in the stationary bore hole (39) so as to engage radiallytherein, wherein the guide strip (31) and guide groove (40) each havecontours having a pitch corresponding to the pitch of a respectivehelical toothing (8; 9; 10).
 2. The device according to claim 1,additionally comprising a controllable rotary motor (26) for activelyrotating said pressure die (27).
 3. The device according to claim 1,wherein the guide strip (31) engages in the guide groove (40) when therotary guide (29) is moved in.
 4. A device for producing a transmissionshaft according to claim 1 by spin welding, comprising a first rotatablereceptacle (25) for an adjacent hollow shaft portion (2; 3; 4) which isin driving connection with a controllable rotary drive (26) and acontrollable brake (37) for plasticizing the facing contact surfaces(11, 12; 13, 14; 15, 16) of the two adjacent hollow shaft portions (2,3; 3, 4; 4; 5).
 5. A device for producing a transmission shaft accordingto claim 1 by electric arc welding with magnetically controlled arcs,comprising a second receptacle (25) for an adjacent hollow shaft portion(2; 3; 4) and an annular pole-and-coil arrangement (38) for plasticizingthe facing contact surfaces (11, 12; 13, 14; 15, 16) of the two adjacenthollow shaft portions (2, 3; 3, 4; 4; 5).